1. Field of the Invention
This invention relates to a composite circuit element, and more particularly relates to a chip-type composite bead element in which, for example, a filter circuit is formed.
2. Description of the Prior Art
Pins of an integrated circuit ( IC ) are generally connected to external circuits through filter elements which are in the form of a bead or the like. Such filter elements will interfere with each other when they are mounted to IC pins which are closely arranged unless they are made as small as possible. Hence, in order to provide smaller pin spacings, miniaturization of filter elements is mandatory. Inductors and capacitors are necessary as minimum components of a filter element, and the requirement for miniaturization can not be achieved unless these components are made compact. For example, a filter element shown in FIG. 1 comprises four coils L1, L2, L3 and L4, and a capacitor C. The filter element formed by discrete coils and capacitor will result in a large size, hence it is necessary to provide the filter element in form of a composite chip. As one aspect of the miniaturization, the present applicant has filed a Japanese Utility Model Application on a proposal in which the regions of inductors consist of a single magnetic body ( The application has not been laid open at the moment of the present application ). FIGS. 2 and 3 show the outline of the proposal. That is, a plurality of feed-through holes are provided in a magnetic body 1 which is formed by a magnetic ferrite having a high magnetic permeability, and a conductor 3 is inserted through the adjacent feed-through holes successively from the opposite direction to make the surroundings of each feed-through hole an equivalent bead inductor.
In the above-described configuration, inductors are unified in a composite body to achieve miniaturization, but it is necessary to mount capacitors on a surface of the magnetic body 1. Hence, the total thickness of the filter circuit component is still large, and accordingly it is impossible to satisfactorily answer the requirement of reduction fo pin spacings due to miniaturization of IC's.